#include "stdio_impl.h"
#include "locale_impl.h"
#include <wchar.h>
#include <errno.h>

static wint_t __fgetwc_unlocked_internal(FILE *f)
{
    wchar_t wc;
    int c;
    size_t l;

    /* Convert character from buffer if possible */
    if (f->rpos != f->rend) {
        l = mbtowc(&wc, (void *)f->rpos, f->rend - f->rpos);
        if (l+1 >= 1) {
            f->rpos += l + !l; /* l==0 means 1 byte, null */
            return wc;
        }
    }

    /* Convert character byte-by-byte */
    mbstate_t st = { 0 };
    unsigned char b;
    int first = 1;
    do {
        b = c = getc_unlocked(f);
        if (c < 0) {
            if (!first) {
                f->flags |= F_ERR;
                errno = EILSEQ;
            }
            return WEOF;
        }
        l = mbrtowc(&wc, (void *)&b, 1, &st);
        if (l == -1) {
            if (!first) {
                f->flags |= F_ERR;
                ungetc(b, f);
            }
            return WEOF;
        }
        first = 0;
    } while (l == -2);

    return wc;
}

wint_t __fgetwc_unlocked(FILE *f)
{
    locale_t *ploc = &CURRENT_LOCALE, loc = *ploc;
    if (f->mode <= 0) fwide(f, 1);
    *ploc = f->locale;
    wchar_t wc = __fgetwc_unlocked_internal(f);
    *ploc = loc;
    return wc;
}

wint_t fgetwc(FILE *f)
{
    wint_t c;
    FLOCK(f);
    c = __fgetwc_unlocked(f);
    FUNLOCK(f);
    return c;
}

weak_alias(__fgetwc_unlocked, fgetwc_unlocked);
weak_alias(__fgetwc_unlocked, getwc_unlocked);
